I have one of those little yellow chrono's. You can pick them up cheap for like $40. They have no ROF option and you have to clear it after every shot, but it lets me tech my stuff for pretty cheap. A Virtue Clock would be awesome, but I'm not dropping $185 for one.

A virtue clock woukd be ideal. They clock fps and bps, as well as having the unique ability to store 15 shots on memory. So you can rip a 15 ball rope through there and look back to see if you are getting any drop off, inconsistency etc. Virtue also stated thwy will be releasing some updates, so you can plug the chip into your pc, view graphs of shots etc. At 185 it is a little steep, but well worth it IMO. Thats why im looking to pick.one up.

PS2 chronograph, only $54 shipped, I'm waiting on mine to arrive now. Figured for that price for what it claims to do, it's worth a shot. Supposed to be as accurate as the shooting chrony and counts both fps and bps. up to 4200 fps, so for your other guns its useful too. Not really handheld, but figured it was worth mentioning. If all you need it for is to fine tune your marker, then I would go for more accuracy than for handheld. Plus the little yellow one doesn't read bps if that is also what you're tuning for.